Two official composition tables disagree about Jerusalem artichoke. The Swiss Food Composition Database credits it with 12.1 g of dietary fibre per 100 g raw; the French ANSES Ciqual table counts 2.1 g and files 9.6 g under sugars. This is not an error. It is the same molecule, inulin, counted two different ways, and that gap alone explains why Jerusalem artichoke is simultaneously the most interesting tuber on this list and the one that sends the most people to the bathroom.

That is where this page starts. What these vegetables actually deliver, measured rather than celebrated; what cooking takes away from them; and the two or three concrete things worth knowing before you buy three kilos because they looked lovely at the market.

Jerusalem artichoke and the inulin question

Inulin is a fructan, a chain of fructose molecules that the human small intestine cannot break down for lack of the necessary enzyme. It passes through intact and arrives in the colon, where bacteria ferment it. That is why it counts as fibre: functionally, it behaves like one.

The two tables treat it differently because the analytical methods differ. The classic enzymatic-gravimetric method does not retain low degree-of-polymerisation fructans, which pass into the filtrate and end up counted with the sugars; chromatographic methods measure them specifically and file them under fibre. Hence 2.1 g on one side and 12.1 g on the other for the same tuber.

For a reader, the practical consequence matters more than the methodological argument. Those 9 to 12 g of fermentable material per 100 g do reach the colon, whichever box the table puts them in. A 150 g portion of Jerusalem artichoke, roughly a small plate of roasted tubers, therefore delivers between 14 and 18 g of fermentable substrate depending on which table you use. For comparison, the protocol of the LEONORA clinical trial, published in BMC Cancer in 2026, raises inulin in two-week steps from 3 g to 10 g per day, with the explicit rationale of training the microbiome gradually and avoiding flatulence. One plate of Jerusalem artichokes exceeds that trial’s highest step.

This is neither dangerous nor a reason to avoid them. It is a reason to start with 80 g rather than 300, and not to serve Jerusalem artichoke soup as a starter at a meal where you care about the conversation.

As for the rest of its composition, raw Jerusalem artichoke comes in at 54 kcal per 100 g in the Swiss database, with 2.4 g of protein, 530 mg of potassium and 7.3 mg of vitamin C. Those 530 mg of potassium represent 26.5 % of the 2000 mg nutrient reference value set in Annex 10 of the Swiss food information ordinance, well past the 15 % threshold that defines a significant amount. It is this tuber’s strongest number, and a useful complement to the intakes described in our complete guide to plant proteins.

Watch out for boiling, though: the Swiss database records 250 mg of potassium per 100 g of Jerusalem artichoke cooked without salt, against 530 mg raw. Potassium is water soluble and leaves in the cooking water. Roasting, steaming, or a soup whose broth you actually eat keep what boiling and draining throws away.

Preparation

Scrub them under cold water, vigorously, working into the folds where soil clings. The skin is thin and edible: peeling wastes time and flesh, and changes nothing about digestive tolerance, since the inulin is in the flesh rather than the skin.

Once cut, they oxidise within minutes. A squeeze of lemon in the holding water keeps them pale.

To roast: 2 to 3 cm wedges, one tablespoon of oil per 500 g, 200 °C for 30 to 35 minutes, turning halfway. They are done when a knife tip enters without resistance and the edges have browned. Temperature matters: below 180 °C they cook without browning and stay floury.

Parsnip loses half its vitamin C in water

Raw parsnip contains 19.7 mg of vitamin C per 100 g in the Swiss database, which is 24.6 % of the 80 mg reference value. That clears the significant-amount threshold. Cooked without salt, it drops to 8.3 mg, or 10.4 %, below the threshold. Potassium follows the same curve: 430 mg raw, 200 mg cooked.

Ciqual measures different absolute values, 11.5 mg of vitamin C raw and 13 mg cooked, but there the cooking method changes everything: parsnip stewed in its own moisture keeps 510 mg of potassium per 100 g, against 367 mg for boiled parsnip. The lesson is identical in both tables: what leaves, leaves in the water.

Hence one simple rule for every root vegetable on this page. Roast, stew covered, steam, or make a soup whose broth you drink. Boiling in plenty of water that then goes down the sink is the only method that genuinely costs you something. Belgian work published in 2018 in the International Journal of Food Sciences and Nutrition, covering 29 vegetables, points the same way for fructans: steaming preserves them without reducing their degree of polymerisation, and simply shifts part of the insoluble fibre towards high-molecular-weight soluble fibre in 18 of the 29 vegetables tested.

On fibre the tables diverge less: 2.1 g per 100 g in the Swiss database, 4.7 g in Ciqual. Either way parsnip sits below the 6 g per 100 g that would license the “high fibre” claim under Annex 13, and around or above the 3 g that licenses “source of fibre” depending on the table.

Parsnip’s sweetness comes from its free sugars, 3.1 g per 100 g in the Swiss database and 4.8 g in Ciqual, which concentrate under dry heat and caramelise. That is why roasted parsnip tastes of something that boiled parsnip does not.

About the furanocoumarins

Parsnip belongs to the Apiaceae and contains furanocoumarins: bergapten, xanthotoxin, imperatorin, psoralen. These are photosensitising molecules, and a 2024 review in the journal Life on phytophotodermatitis explicitly names Pastinaca sativa among the documented phototoxic species, alongside giant hogweed and fig.

The mechanism is straightforward: sap on the skin, followed by ultraviolet exposure, triggers a non-immune skin reaction with redness, blistering and persistent hyperpigmentation. It is not an allergy and has nothing to do with eating the vegetable.

Two points keep this in proportion. First, a 2026 review in Food Science and Nutrition on parsnip composition notes that the cultivated variety carries reduced furanocoumarin levels compared with its wild form. Second, the documented cases involve handling quantities in the sun, typically gardening or harvesting, not peeling three roots in a kitchen.

In practice: if you harvest or peel a lot of parsnip outdoors on a sunny day, wear gloves and wash your forearms. Indoors the question does not arise.

Preparation

Peel it if the skin looks dull or marked, otherwise a thorough scrub will do. In a large parsnip the core turns fibrous and woody: halve the root lengthways and cut that core out, because no amount of cooking will soften it.

To roast: 1.5 cm batons, oil, 200 °C, 25 to 30 minutes. Thin batons burn before they cook through, large chunks stay raw at the centre; even thickness matters more than timing.

Pattypan is a summer squash

Pattypan is a variety of Cucurbita pepo, the same species as courgette, and its composition follows: the Swiss database gives 17 kcal per 100 g of raw courgette, 1.1 g of fibre, 260 mg of potassium and 14.8 mg of vitamin C. Neither the Swiss table nor Ciqual carries a “pattypan” entry, and courgette values are the most defensible approximation.

What follows from that botanical kinship is more useful than a table. Pattypan is a summer squash, harvested young, thin skinned, keeping one to two weeks rather than several months like a winter squash. It is more than 90 % water, with a direct kitchen consequence: it releases a lot of liquid and dilutes whatever you put around it.

Hence one cooking rule that solves most of the problem. Salt the cubes or slices, let them drain in a colander for twenty minutes, pat dry, then sear over high heat in a single layer without stirring for the first three minutes. Pattypan crowded into a lukewarm pan boils in its own juice and ends up bland and soggy, which is the most common complaint about it.

Choose them small, roughly hand sized. Beyond that the skin hardens, the seeds develop and the flesh turns cottony. A young pattypan cooks with its skin on; a large one has to be peeled, and peeling a scalloped shape is a chore that should put you off buying it.

The others, and what they actually deliver

Black salsify, or scorzonera, is the most remarkable of this group on one specific count: the Swiss database measures 18.5 g of dietary fibre per 100 g raw. That is three times the 6 g threshold licensing the “high fibre” claim, and more than most cooked legumes. Ciqual, with its different method, counts 3.3 g for raw black salsify, and the gap reflects the same analytical question as Jerusalem artichoke, since scorzonera is likewise inulin rich. Whichever table you take, it is a vegetable to introduce gradually.

Worth knowing too: scorzonera exudes a sticky white latex when cut, which blackens fingers and utensils. Gloves, a peeler and a bowl of acidulated water settle it.

Swede is the quiet vitamin C champion: 33 mg per 100 g raw in Ciqual, or 41 % of the reference value, more than parsnip and far more than Jerusalem artichoke. Cooked it falls to 18.8 mg, still 23.5 % of the reference value and therefore above the significant-amount threshold. A secondary benefit, but a real one, given that vitamin C improves the absorption of plant iron, as our page on plant iron absorption explains.

Chinese artichoke is the weakest of the set nutritionally, at 50.8 kcal, 2.1 g of protein and 1.9 g of fibre per 100 g cooked in Ciqual. You cook it for its crisp texture and hazelnut scent rather than its nutrients, and that is reason enough.

Tuberous chervil has no entry in either the Swiss database or Ciqual. No reliable published figures exist for this tuber in the French and Swiss reference tables. That does not stop it being excellent roasted; it only stops anyone from asserting anything about its composition.

The table, verifiable values only

Values per 100 g raw unless stated. Percentages refer to the nutrient reference values in Annex 10 of the Swiss ordinance: potassium 2000 mg, vitamin C 80 mg.

Vegetable	Energy	Fibre	Potassium	% NRV K	Vitamin C	% NRV C	Source
Jerusalem artichoke	54 kcal	12.1 g	530 mg	26.5 %	7.3 mg	9.1 %	Swiss
Jerusalem artichoke	60.7 kcal	2.1 g	495 mg	24.8 %	5 mg	6.3 %	Ciqual
Parsnip	62 kcal	2.1 g	430 mg	21.5 %	19.7 mg	24.6 %	Swiss
Parsnip, cooked	58 kcal	2.1 g	200 mg	10 %	8.3 mg	10.4 %	Swiss
Black salsify	54 kcal	18.5 g	240 mg	12 %	4.9 mg	6.1 %	Swiss
Swede	-	2.6 g	349 mg	17.5 %	33 mg	41.3 %	Ciqual
Chinese artichoke, cooked	50.8 kcal	1.9 g	310 mg	15.5 %	-	-	Ciqual
Courgette (pattypan proxy)	17 kcal	1.1 g	260 mg	13 %	14.8 mg	18.5 %	Swiss
Carrot (benchmark)	42 kcal	2.7 g	220 mg	11 %	3.1 mg	3.9 %	Swiss

Two things jump out. Jerusalem artichoke and black salsify play in a different league on fibre, provided you accept the Swiss way of counting inulin. And swede, the least glamorous item on the list, supplies the most vitamin C of the lot.

Introducing fructans without regretting it

The most useful thing on this page is a method, because first-market enthusiasm is exactly what puts people off Jerusalem artichoke for a decade.

Start with 80 g of Jerusalem artichoke or black salsify per person, no more, mixed with other vegetables in a roasting tray. Wait two or three days before repeating, and increase in steps, the way the LEONORA protocol does with its two-week increments. Tolerance builds: the bacteria capable of fermenting inulin multiply when you supply it regularly, and the symptoms of the first few attempts fade for most people.

Drink water. Soluble fibre holds water in the colon, and a sudden increase in fibre without a matching fluid intake produces the opposite of the intended effect.

If you are following a low-FODMAP protocol for irritable bowel syndrome, these vegetables are not for you during the restriction phase: Jerusalem artichoke and black salsify are, by definition, fructan concentrates. They can return during reintroduction, tested individually. Our page on the low-FODMAP diet and vegetarianism sets out the approach.

To frame the stakes: the NHS recommends 30 g of fibre a day and records an average adult intake of about 20 g. A 150 g portion of Jerusalem artichoke closes that gap on its own, by the Swiss table. That is the best reason to eat these vegetables, and precisely the reason to go gently.

Why they disappeared, and what the usual story misses

The explanation you read everywhere fits in one sentence: Jerusalem artichoke and swede were dropped because they recalled wartime deprivation. Partly true, and insufficient.

The real driver is agricultural and commercial. These vegetables suit modern distribution badly. Jerusalem artichoke has a knobbly, irregular shape full of folds that makes industrial washing and grading difficult, and its thin skin dehydrates quickly. Black salsify is a long, brittle root that snaps during mechanical harvest. Pattypan, with its scalloped outline, does not stack in a crate. Parsnip mainly suffered direct competition: potato occupies the same place on the plate, keeps better, yields more per hectare and requires no explanation to the shopper.

In other words, these vegetables were not judged bad. They were judged impractical by a supply chain that rewards regular formats, long storage and yield. What brings them back today is not nostalgia either: it is direct sales, veg boxes and markets, where irregular shape no longer costs anything.

That has a practical consequence. You will find them more easily and in better condition from a grower or a veg box than in a supermarket aisle, where they often appear undersized, already dehydrated, or priced according to their novelty status rather than their production cost.

Season, buying, storage

In Switzerland, Jerusalem artichoke, parsnip, black salsify, swede and Chinese artichoke are autumn and winter vegetables, broadly available from October to March, peaking after the first frosts convert some of the starch into sugars and make the roots sweeter. Pattypan is the exception: a summer squash, harvested July to September.

When buying, look for firm roots that do not bend under thumb pressure. A wrinkled Jerusalem artichoke has lost its water and will peel badly. A parsnip whose thin end is soft or blackened is on the turn. A scorzonera already snapped in the crate oxidises through the break and bleeds its latex.

These vegetables arrive from the field with soil on them, and that is good news: the soil protects them from drying out. Only wash them when you are about to cook. In the fridge drawer, in a paper bag or a slightly damp cloth, the roots hold two to three weeks, pattypan only one to two.

Freezing works for the roots provided you blanch them for three minutes first, which deactivates the enzymes responsible for browning. Raw frozen pattypan releases too much water on thawing; better to cook it and freeze the finished dish. Our guide to batch cooking winter soups applies these principles across seasonal vegetables, and our anti-waste practices cover dehydrating and lacto-fermenting, both of which work well on roots.

Three ways of cooking them that work

The mixed roasting tray. 600 g of assorted roots in evenly sized pieces, 2 tablespoons of oil, salt, thyme, 200 °C, 35 to 40 minutes, turning halfway. It is the most forgiving method: dry heat concentrates the sugars and papers over quality differences between vegetables. Serve with a legume to make it a complete meal.

The soup whose broth you eat. Sweat the vegetables in a little oil for ten minutes, cover with water, simmer twenty minutes, blend with the liquid. The potassium and vitamin C that left the vegetable stay on the plate, which is not the case when you boil and drain. A spoonful of almond butter or plant cream at the end supplies the fat that carries the aromas.

The blended mash. Two thirds potato, one third parsnip or swede, cooked together in salted water then crushed with a fork rather than a blender, on pain of elastic mash. Parsnip alone gives a mash too sweet for most palates; that is the most common mistake with this vegetable. A spoonful of nutritional yeast off the heat offsets the sweetness with a savoury note and no added salt.

Our essential spices and herbs for vegetarian cooking fills in the seasoning side.

What goes with what

These vegetables share one flavour trait: they are sweet, most of them sweeter than carrot. A plate made entirely of roasted roots turns cloying fast, and that is why people give up after two attempts.

Three families of ingredients fix it. Acid first: cider vinegar, lemon juice, a spoonful of mustard in the dressing, or capers over roasted slices. Bitterness next, with rocket, radicchio or lightly toasted walnuts. And salty-fermented, a dab of miso or chopped olives, which pulls the whole thing down and stops it tipping into dessert.

On aromatics, roots take robust herbs, thyme, rosemary, bay, which survive a long spell in the oven. Delicate fresh herbs, parsley, coriander, dill, go in out of the oven at the last moment. Cumin and caraway work particularly well on swede and parsnip, tempering their sweetness.

Pattypan, less sweet and more neutral, wants the opposite: it needs flavour brought to it rather than corrected. Garlic, chilli, fresh herbs in quantity, and a well-defined cheese or plant alternative.

Five common mistakes

Serving a large portion of Jerusalem artichoke the first time. Between 14 and 18 g of fructans at once, on a microbiome unused to them, produces a predictable result.

Boiling in plenty of water and pouring it away. Parsnip leaves more than half its vitamin C and more than half its potassium in there.

Buying big pattypans. The skin hardens, the flesh turns cottony and peeling a scalloped shape is thankless.

Peeling Jerusalem artichokes. The skin is thin and edible, peeling wastes time and flesh, and changes nothing digestively.

Leaving the woody core in a large parsnip. No cooking softens it and it will come out fibrous on the plate.

Depending on your situation

You have never eaten Jerusalem artichoke. Start with 80 g, roasted, mixed with other vegetables. Build up over several weeks.

You have a sensitive gut or irritable bowel syndrome. Swede, Chinese artichoke, parsnip and pattypan are far more tolerable than Jerusalem artichoke and black salsify, the two most fructan-rich items on the list.

You are after vitamin C in winter. Swede, at 33 mg per 100 g raw, beats everything else here, and retains 18.8 mg after cooking.

You garden or harvest your own. Wear gloves when handling parsnip in quantity in the sun, because of the furanocoumarins in the sap.

You are cooking for children. Roasted parsnip and pan-fried pattypan are the two easiest entry points, sweet and free of bitterness. Jerusalem artichoke, with its digestive effects, is a poor first attempt.

Frequently asked questions

Why do the tables disagree on Jerusalem artichoke fibre? Because they count inulin differently. The Swiss method files it under fibre, giving 12.1 g per 100 g; Ciqual’s method puts much of it under sugars, leaving 2.1 g of fibre and 9.6 g of sugars.

Does Jerusalem artichoke really cause bloating? It delivers a lot of fermentable material, between 14 and 18 g in a 150 g portion. Tolerance builds with gradual introduction.

Should I peel Jerusalem artichokes? No. The skin is thin and edible, a thorough scrub is enough.

Is parsnip dangerous to handle? Its sap contains photosensitising furanocoumarins, and the cultivated variety carries less than the wild form. The risk applies to handling quantities in the sun, not to peeling in a kitchen.

How do I stop pattypan releasing water? Salt it, drain for twenty minutes, pat dry, then sear over high heat in a single layer without stirring for the first three minutes.

Which one supplies the most vitamin C? Swede, at 33 mg per 100 g raw in Ciqual, which is 41 % of the reference value.

Can I freeze these vegetables? The roots, yes, after three minutes of blanching. Raw pattypan freezes badly; cook it first.

Are these vegetables more nutritious than carrot? On potassium and fibre, yes, markedly so for Jerusalem artichoke and black salsify. On vitamin C, swede and raw parsnip beat carrot by an order of magnitude.

Limits of this page

The values come from two composition tables, the Swiss BLV database and the ANSES Ciqual table, whose divergence on fructans is explained above and illustrates a general limit of such data: these are averages, sensitive to variety, soil, harvest date and storage time. Pattypan and tuberous chervil have no entry in either table; the figures given for pattypan are those of courgette, the same botanical species, and no figures are advanced for tuberous chervil. The regulatory thresholds quoted come from the Swiss food information ordinance and govern commercial claims, not home cooking. The inulin introduction steps draw on the protocol of a trial run in patients operated on for colorectal cancer, used here as a prudence benchmark rather than a clinical recommendation. This page does not replace medical advice, particularly for digestive disease or kidney impairment, where potassium intake needs supervision.

Sources

• Swiss Food Composition Database
• Ciqual food composition table, ANSES
• Swiss ordinance on food information (RS 817.022.16)
• NHS, how to get more fibre into your diet
• LEONORA trial protocol, BMC Cancer 2026
• Fructans and fibre in raw and steamed vegetables, Int J Food Sci Nutr 2018
• Composition and phytochemistry of Pastinaca sativa, Food Sci Nutr 2026
• Phytophotodermatitis induced by phototoxic plants, Life 2024
• Extraction and characterisation of Jerusalem artichoke inulin, Scientific Reports 2026